1. Field of the Invention
The invention relates to a cord-releasing safety device, more particularly to a cord-releasing safety device for a window blind.
2. Description of the Related Art
Generally, a window blind includes a pull cord having one end connected to a connecting device which is installed on the window blind and another end fixed to a headrail of the window blind. A user pulls the pull cord so as to lower or raise a blind body of the window blind. However, since a suitable force to pull the pull cord cannot be controlled, and since it is possible for the pull cord to become stuck, the user frequently pulls excessively on the pull cord. This may result in pulling down the headrail or in damaging the connecting device.
Referring to FIGS. 1 and 2, a releasable cord connection apparatus 101, as disclosed in U.S. Pat. No. 6,431,248, is shown to include a receptive member 13, and a connective member 14 that is inserted releasably into the receptive member 13. The receptive member 13 has a first section 131 coupled to a headrail 11 of a window blind 100, and a second section 133 perpendicular to the first section 131 and having a recess 132. The connective member 14 is substantially V-shaped, and has a semi-arcuate end 142, and two elongate pieces 141 extending away from the semi-arcuate end 142 and inserted releasably into the recess 132. A cord 10 has one end tied to the semi-arcuate end 142 of the connective member 14.
When an excessive force is applied to the cord 10, the connective member 14 releases from the recess 132 so that the headrail 11 is prevented from being pulled down by the cord 10. However, since the elongate pieces 141 of the connective member 14 are not provided with means by which to undergo damping, when an excessive force is applied to the cord 10, the connective member 14 either releases suddenly from the recess 132, or remains stuck in the recess 132 at a nearly-released position such that in the next pulling operation, the connective member 14 is too easily released from the recess 132. Since the releasable cord connection apparatus 101 is not provided with any damping means, any force applied to the cord 10 can be transmitted to the headrail 11 without attenuation.
Referring to FIG. 3, a cord member safety connector 102 for a window blind, as disclosed in U.S. Pat. No. 6,845,803, is shown to be similar to the aforementioned releasable cord connection apparatus 101, and includes a supporting member 15 and a coupling member 16. The supporting member 15 includes a solid base 153 having a cylindrical through hole 152, and a flat mounting flange 151 extending perpendicularly from a periphery of a top side of the solid base 153 and fastened to the headrail 11 of the window blind 100 (see FIG. 1). The coupling member 16 includes a top portion 161 and a bottom portion 163. The top portion 161 is provided with an expanded top split head 162 having a diameter slightly greater than that of the cylindrical through hole 152 and press-fitted into the cylindrical through hole 152. The cord 10 has one end tied to the bottom portion 163 of the coupling member 16.
When the user excessively pulls the cord 10, the top portion 161 of the coupling member 16 releases from the cylindrical through hole 152. However, the cord member safety connector 102 is similarly not provided with a damping means such that the coupling member 16 is released from the cylindrical through hole 152 in a sudden manner.
Referring to FIGS. 4 and 5, a window covering cord safety assembly 103, as disclosed in U.S. Pat. No. 6,263,946, is shown to include a housing 17, an operating cord 18, and a damping unit 19. The housing 17 has a plurality of through holes 171 formed in a top closed-end portion thereof. The operating cord 18 has one end extending into the housing 17, and is operable to move the housing 17. The damping unit 19 includes a retainer 191 disposed in the housing 17, a coiled spring 192 disposed between a top portion of the retainer 191 and the top closed-end portion of the housing 17, a plurality of control cords 193 extending through the respective through holes 171 and along a periphery of the retainer 191, and a plurality of eyelets 194 connected respectively to lower ends of the control cords 193 and retained on a bottom portion of the retainer 191.
When the user excessively pulls the operating cord 18, the housing 17 moves downwardly first, and compresses the coiled spring 192, so that the pulling force transmitted to the headrail (not shown) is attenuated. In addition, through compression of the coiled spring 192, the user can feel that a larger pulling force is necessary to pull the cord 18. This feeling will warn the user that a maximum tolerance for the pulling force is nearly reached. If the user releases the operating cord 18 at this stage, the coiled spring 192 biases the housing 17 together with the operating cord 18 to move upwardly. If the operating cord 18 is pulled further, the control cords 193 and the eyelets 194 will move past the periphery of the retainer 191 and escape from the through holes 171, as shown in FIG. 5.
Although the window covering cord safety assembly 103 can achieve its intended purpose, it has a very complicated structure so that it has a relatively high production cost and a relatively long production time. Further, when the control cords 193 and the eyelets 194 are removed from the housing 17, a substantial amount of time is required to install them back into the housing